Edges

I was wondering how you get the edges of a "blanket" that goes on top of an already fondant covered cake to look scalloped or rounded on the edges? Does anyone know what I mean? I tried to do this the other day for a cake and used the circular fondant cutter around the edges of a rolled out, circular piece of fondant, and it didn't turn out right and it was lopsided. Anyone have some suggestions? Is there a special tool you should use?

I bought the Wilton pastry wheel for cutting my fondant, works much better than the plastic ones available. It has 2 wheels on it, one is straight and the other is fluted, makes a nice edge on fondant and is easy to use.